1. Field of the Invention
The present invention relates to an electron emission device, an electron emission display apparatus that uses the electron emission device, and a method of manufacturing the same, and more particularly, to an electron emission device having a structure in which a voltage applied to an electron emission source is uniformly distributed, an electron emission display apparatus having the electron emission device to increase brightness uniformity of pixels, and a method of manufacturing the same.
2. Description of the Related Art
Generally, electron emission devices use a thermal cathode or a cold cathode as an electron emission source. Electron emission devices that use the cold cathode method include field emitter array (FEA) type devices, surface conduction emitter (SCE) type devices, metal insulator metal (MIM) type devices, metal insulator semiconductor (MIS) type devices, ballistic electron surface emitting (BSE) type devices, etc.
A field emitter array type electron emission device uses the principle that, when a material having a low work function or a high β function is used as an electron emission source, the material readily emits electron in a vacuum due to electric potential. Devices that employ a tapered tip structure formed of, for example, Mo, Si as a main component, a carbon group material such as graphite, diamond like carbon (DLC), etc., or a nano structure such as nanotubes, nano wires, etc., have been developed.
In a surface conduction emitter type electron emission device, an electron emission source includes a conductive thin film having micro cracks between first and second electrodes facing each other on a substrate. The electron emission device makes use of the principle that electrons are emitted from the micro cracks which are electron emission sources, when a current flows on the surface of the conductive thin film by applying a voltage to the electrodes.
The metal insulator metal type electron emission devices and metal insulator semiconductor type electron emission devices make use of the principle of emitting electrons that, after the MIM and MIS type electron emission devices respectively form a metal-dielectric layer-metal (MIM type) structure and a metal-dielectric layer-semiconductor (MIS type) structure, when a voltage is applied to two metals having a dielectric layer therebetween or to a metal and a semiconductor, electrons migrate from the metal or the semiconductor having a high electron potential to the metal having a low electron potential.
A ballistic electron surface emitting type electron emission device includes an electron emission source making use of a principle that electrons travel without scattering when the size of a semiconductor is smaller than a mean-free-path of electrons in the semiconductor. To form the electron emission source, an electron supply layer formed of a metal or a semiconductor is formed on an ohmic electrode, and an insulating layer and a metal thin film are formed on the electron supply layer. When a voltage is applied between the ohmic electrode and the metal thin film, the electron emission source emits electrons.
The field emitter array type electron emission devices can be classified into top gate devices and bottom gate devices according to the location of a cathode and a gate electrode, and can be classified into diodes, triodes, tetrodes, etc. according to the number of electrodes they include.
The conventional electron emission display apparatus includes an electron emission device and a front panel, which are located parallel to each other and form a vacuum space, and a spacer that maintains a gap between the electron emission device and the front panel.
The electron emission device includes a first substrate, a plurality of gate electrodes and a plurality of cathodes crossing the gate electrodes on the first substrate, and an insulating layer which is located between the gate electrodes and the cathodes and electrically insulates the gate electrodes from the cathodes.
A plurality of electron emission holes are formed on regions where the gate electrodes cross the cathodes. An electron emission source is formed in each of the electron emission holes.
The front panel includes a second substrate, an anode located on the lower surface of the second substrate, and a plurality of phosphor layers located on the lower surface of the anode.
A display apparatus that displays an image using a FEA type electron emission device often has non-uniform brightness between pixels which may occur due to variation in the voltages applied to respective electron emission source. The non-uniformity in brightness between pixels greatly impairs the quality of the image, and thus, the non-uniformity in brightness of pixels must be prevented. Accordingly, there is a need to solve the problem of non-uniformity of pixels.